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serial: amba-pl011: drop low-latency workaround

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Commit ead76f329f ("ARM: 6763/1: pl011: add optional RX DMA to PL011
v2") added RX DMA support and also reproduced the workaround for the
infamous low_latency behaviour of tty_flip_buffer_push() by dropping and
reacquiring the port lock during receive processing.

Since commit a9c3f68f3c ("tty: Fix low_latency BUG"),
tty_flip_buffer_push() always schedules a work item to push data to the
line discipline and there's no need to keep any low_latency hacks around.

Note that the port lock is also dropped in the PIO path
(see pl011_rx_chars), but it is not clear whether this is still needed
by the DMA code added by the aforementioned commit.

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Russell King <linux@armlinux.org.uk>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210421095509.3024-6-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2021-04-21 11:54:48 +02:00 committed by Greg Kroah-Hartman
parent 173d37fc59
commit 02d5364007
1 changed files with 0 additions and 2 deletions
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2
drivers/tty/serial/amba-pl011.c
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@ -937,12 +937,10 @@ static void pl011_dma_rx_chars(struct uart_amba_port *uap,
fifotaken = pl011_fifo_to_tty(uap);
}
spin_unlock(&uap->port.lock);
dev_vdbg(uap->port.dev,
"Took %d chars from DMA buffer and %d chars from the FIFO\n",
dma_count, fifotaken);
tty_flip_buffer_push(port);
spin_lock(&uap->port.lock);
}
static void pl011_dma_rx_irq(struct uart_amba_port *uap)